Several transition metal complexes based upon bis-imine pyridine ligands have been reported in the art, in particular for use in catalyst systems for the catalysis of ethylene and/or olefin (co-) polymerization and (co-) oligomerization reactions as well as for use in catalyst systems for the catalysis of alpha-olefin dimerization reactions.
In this regard a number of published patent applications describe catalyst systems for the polymerization or oligomerization of 1-olefins, in particular ethylene, which contain nitrogen-containing transition metal compounds. See, for example, the following patent applications which are incorporated herein by reference in their entirety: WO 92/12162, WO 96/27439, WO 99/12981, WO 00/50470, WO 98/27124, WO 99/02472, WO 99/50273, WO 99/51550, EP-A-1,127,987, WO 02/12151, WO 02/06192, WO 99/12981, WO 00/24788, WO 00/08034, WO 00/15646, WO 00/20427, WO 01/58874 and WO 03/000628.
In particular, recently published Shell applications WO01/58874, WO02/00339, WO02/28805 and WO 03/011876, all of which are incorporated herein by reference in their entirety, disclose novel classes of catalysts based on bis-imine pyridine iron compounds which are highly active in the oligomerization of olefins, especially ethylene and which produce linear alpha olefins in the C6-C30 range with a Schulz-Flory distribution, said linear alpha olefins being of high purity.
In co-pending PCT Patent Application No. PCT/EP03/10708 (now published as WO 2004/037415), there is described a catalyst system for the oligomerization of ethylene to linear alpha olefins, wherein the catalyst system comprises:
a) one or more bis-arylimine pyridine iron or cobalt catalysts;
b) a first co-catalyst compound which is selected from aluminium alkyls, aluminoxanes, and mixtures thereof; and
c) one or more additional co-catalyst compounds which comprises one or more compounds of the formula ZnR′2 wherein each R′, which may be the same or different, is selected from hydrogen, optionally substituted C1-C20 hydrocarbyl, phenyl, Cl, Br, I, SR″, NR″2, OH, OR″, CN, NC wherein R″, which within the same molecule may the same or different, is C1-C20 hydrocarbyl.
Co-pending PCT Patent Application No. PCT/EP03/10708 (now published as WO 2004/037415) describes bis-arylimine pyridine ligands having the formula below:

wherein X is carbon or nitrogen,
n is 0 or 1,
m is 0 or 1,
Z is a π-coordinated metal fragment,
R1-R5, R7-R9 and R12-R14 are each, independently, hydrogen, optionally substituted hydrocarbyl, an inert functional group, or any two of R1-R3, R7-R9 and R12-R14 vicinal to one another taken together may form a ring; R6 is hydrogen, optionally substituted hydrocarbyl, an inert functional group, or taken together with R7 or R4 to form a ring; R10 is hydrogen, optionally substituted hydrocarbyl, an inert functional group, or taken together with R9 or R4 to form a ring; R11 is hydrogen, optionally substituted hydrocarbyl, an inert functional group, or taken together with R5 or R12 to form a ring; and R15 is hydrogen, optionally substituted hydrocarbyl, an inert functional group, or taken together with R5 or R14 to form a ring.
Disclosed within the examples of co-pending PCT Patent Application No. PCT/EP03/10708 (now published as WO 2004/037415) is the 2-[1-(2,4,6-trimethylphenylimino) ethyl]-6-[1-(4-eicosanoxy-3,5-diphenylphenylimino)ethyl]pyridine iron[II] chloride complex, and catalyst systems consisting of 2-[1-(2,4,6-trimethylphenylimino)ethyl]-6-[1-(4-eicosanoxy-3,5-diphenylphenylimino)ethyl]pyridine iron[II] chloride with MAO and 2-[1-(2,4,6-trimethylphenylimino)ethyl]-6-[1-(4-eicosanoxy-3,5-diphenylphenylimino)ethyl]pyridine iron[II] chloride with methylaluminoxane (MAO) and Et2Zn co-catalysts in a toluene solution.
U.S. Pat. No. 6,291,733, describes a method of dimerizing alpha-olefins to mostly linear internal olefin dimers using a catalyst composition comprising a bis-arylimine pyridine iron complex and an alkylaluminoxane co-catalyst composition in molar excess. The reaction of this process proceeds rapidly, even at ambient temperatures, and yields a dimerization product rich in linear internal olefin dimers.
The use of a bis-arylimine pyridine cobalt complex and a modified methylaluminoxane (MMAO) co-catalyst in the dimerization of alpha-olefins is described in the article “Tridentate Cobalt Catalysts for Linear Dimerization and Isomerization of α-Olefins” by Brooke L. Small in Organometallics 2003, 22, 3178-3183. The use of a molar excess of the alkylaluminoxane co-catalyst in this reference makes this process commercially less favourable.
Although catalysts based on bis-arylimine pyridine complexes are useful catalyst precursors in polymerization, oligomerization and dimerization processes, they suffer from the disadvantage that they have low solubility in non-polar media, especially at ambient temperatures. The low solubility of bis-arylimine pyridine complexes in non-polar media such as benzene, toluene and paraffin solvents, especially at ambient temperatures, has several problems attached to it, including difficulty in accurate dosing of the catalyst system into reactors, especially under continuous operation, and damage to the reactor equipment, especially pumps and seals which can be caused by the abrasive action of suspended, non-soluble catalyst particles.
Therefore, there is a need for bis-arylimine pyridine complexes and catalyst systems comprising these complexes which can be used with ease in a continuous process, e.g. continuous polymerization, oligomerization or dimerization process. In particular, there is a need for bis-arylimine pyridine complexes and catalyst systems containing such complexes which are highly soluble in non-polar media, without having a deleterious effect on the catalytic activity displayed by the bis-arylimine pyridine catalyst compositions known in the art.
The present invention provides a transition metal complex based on certain bis-arylimine pyridine ligands and a catalyst system thereof which are highly soluble in non-polar media and display good catalytic activity for continuous polymerization, oligomerization and dimerization processes.